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460 BCE
Democritus
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Period: 460 BCE to
Democritus
His mentor first came up with the atomic theory but it was then adopted by him. He said "The universe is composed of two elements the atoms and the void in which they exist and move".
This then started the theory that atoms were miniscule quantities of matter that are indestructible, homogenous, solid but invisible, and differ in size and shape. -
Dalton
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Period: to
Dalton
Dalton was colorblind and obsessed with particles. Through his experiments he came up with a few new theorys for atoms that some are similar but more advanced then Democritus.
1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) A chemical reaction is a rearrangement of atoms. -
J.J Thompson
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Period: to
J.J Thompson
Discovered the electron by experimenting with a Crookes, or cathode ray, tube. He demonstrated that cathode rays were negatively charged.
In his theory he failed to recognize the positive charges of the atom as particles.
-he also studied positively charged particles in neon gas. -
Period: to
Ruther ford
Created a Gold foil experiment to show how alpha particles exist.
In this experiment they shot alpha particles at gold foil with a zinc sulfide screen behind it. The particles were supposed to show up on the zinc and pass through the gold foil. This demonstrated that the atom has a tiny nucleus because they didnt pass through the foil. -
Period: to
Niels Bohr
He discovered atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922. In 1913 Niels proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. He tested this and then discovered another theory on quantum light. Through various complicated experiments he proved these theories and helped us understand atoms to this day. -
Ruther Ford
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Neils Bohr
